Material-handling apparatus

ABSTRACT

An articulated boom having a single joint intermediate the ends thereof is pivoted at one end about a horizontal axis of a support member. The other end of the boom has end effectors and end effector positioning elements located thereon. A control member smaller in size but similar in form to the articulated boom having a single joint intermediate the ends thereof is also pivoted at one end about another horizontal axis of another support member and a handle is provided at the other end thereof. Means are provided to cause each of the two parts of the articulated boom to follow in orientation a respective one of the two parts of the control member in response to movement of the handle by an operator. Additional means are provided so that forces encountered by the articulated boom are reflected back, reduced in magnitude however, to the handle held by the operator. A pair of assemblies of levers and springs are provided each in cooperative association with a respective part of the control member to counterbalance completely the weight of the unloaded control member and the weight of unloaded boom as reflected by force feedback to the control member.

United States Patent [72] Inventors Ralph S. Mosher;

- Donald A. Kugath, both of Schenectady,

NY. [211 App]. No. 34,159 [22] Filed May 4, 1970 [45] Patented Sept. 28, 1971 [73] Assignee General Electric Company [54] MATERIAL-HANDLING APPARATUS 3 Claims, 7 Drawing Figs. I

[52] 11.8. CI 214/1 CM, 212/35,214/l47R [51] Int. Cl B25j 3/04 [50] Field of Search 214/1 CM,

113V, 1 BD, 147 R;212/35,59

[56] References Cited UNITED STATES PATENTS 3,241,687 3/1966 Orlofi' 214/1 CM 3,280,991 10/1966 Melton 214/1 CM Primary Examiner-Gerald M. Forlcnza Assistant Examiner-George F. Abraham Attorneys-Paul A. Frank, John F. Ahem, Julius J.

Zaskalicky, Frank L. Neuhauser, Oscar B. Waddell and Joseph B. Forman ABSTRACT: Anarticulated boom having a single joint intermediate the ends thereof is pivoted at one end about a horizontal axis of a support member. The other end of the boom has end effectors and end effector positioning elements located thereon. A control member smaller in size but similar in form to the articulated boom having a single joint intermediate the ends thereof is also pivoted at one end about another horizontal axis of another support member and a handle is provided at the other end thereof. Means are provided to cause each of the two parts of the articulated boom to follow in orientation a respective one of the two parts of the control member in response to movement of the handle by an operator. Additional means are provided so that forces encountered by the articulated boom are reflected back, reduced in mag nitude however, to the handle held by the operator.

A pair of assemblies of levers and springs are provided each in cooperative association with a respective part of the control member to counterbalance completely the weight of the unloaded control member and the weight of unloaded boom as reflected by force feedback to the control member.

PATfiNiEn ssPzelsn $608743 smnnra helborne PATENTED SEP28 an SHEET 3 BF 4 MATERIAL-HANDLING APPARATUS The present invention relates in general to material handling apparatus of the kind in which the movements of a control or master member produces corresponding movements amplified in respect to the force exerted thereby of a controlled or slave member and in which a portion of the force ex-- erted by the slave member is reflected back to the master to provide a sense of feel for the force being applied by the slave member and in particular relates to such a manipulator in which means are provided for counterbalancing the unloaded weight of the master and slave members to improve the performance per se thereof as well as to facilitate operator use thereof.

This application is an improvement in the material handling apparatus described and claimed in a copending patent application, Ser. No. 33,442, filed Apr. 30, 1970 and assigned to the assignee of the present application.

An object of the present invention is to provide a manipulator of relatively simple construction and high performance capability.

Another object of the present invention is to provide means for simply counterbalancing the unloaded weight of a manipulator having a slave arm member with bilateral interconnection to the end that the mental and physical capability of an operator can be used to the fullest in fast, efficient, effective control of the slave member of the manipulator to duplicate the motions of the arm of the operator. In carrying out the present invention in accordance with an illustrative embodiment thereof there is provided an articulated'boom having a single joint intennediate the ends thereof and pivoted at one end about a horizontal axis of a support member. The other end of the boom has end effectors and end effector positioning elements located thereon. A control member smaller in size but similar in form to the articulated boom having a single joint intermediate the ends thereof is also pivoted at one end about another horizontal axis of another support member and a handle is provided at the other end thereof. Means are provided to cause each of the two parts of the articulated boom to follow in orientation a respective one of the two parts of the control member in response to movement of the handle by an operator. Additional means are provided so that forces encountered by the articulated boom are reflected back, reduced in magnitude however to the handle held by the operator.

A pair of assemblies of levers and springs are provided, each in cooperative association with a respective part of the control member to counterbalance completely the weight of the unloaded control member and the weight of unloaded boom as reflected by force feedback to the control member for all positions thereof. A spring constant is provided for each assembly which is a function of movement to be balanced and fixed geometric factors. The force applied by the spring of an assembly is made a particular function of geometry and particularly applied to make possible utilization of a fixed spring constant.

The novel features which are believed to be characteristic of the present invention are set forth in the appended claims.

The invention itself, however, together with further objects and advantages thereof may best be understood by reference to the following description taken in connection with the accompanying drawings wherein:

FIG. 1 is a perspective view of a manipulator to which the invention of the present application will be applied.

FIG. 2 is an enlarged perspective view of a portion of the apparatus of FIG. 1 showing the slave or controlled member and the master or control member and the interconnections thereof.

FIG. 3 is a schematic diagram of the hydraulic and electrical systems of the manipulator of FIGS. 1 and 2.

FIG. 4 is an enlarged perspective view similar to the enlarged perspective view of FIG. 2 particularly showing the spring counterbalance assemblies for the upper and lower arm elements of the controlled member.

FIG. 5 is a line diagram of the control member and the slave member of FIG. 1 with the forces acting thereon when unloaded.

FIG. 6 is a-line diagram of the spring counterbalance assembly for the upper control arm element of the control member useful in explaining the operation of the counterbalance assembly as applied in FIG. 4.

FIG. 7 is a line diagram of the spring counterbalance assembly as applied to counterbalancing the forces on the lower arm element of the control member also useful in explaining the application of the spring counterbalance assembly shown in FIG. 4.

The subject matter described in connection with FIGS. 1, 2 and 3 is also described and claimed in a copending application Ser. No. 33,442, filed Apr. 30 1970 and assigned to the assignee of the present invention. FIGS. 1, 2 and 3 and the description thereof are provided to set forth the apparatus to which the counterbalance assemblies of the present application are applied and the manner of application thereto.

Referring now to FIG. 1, there is shown a manipulator 10 having an articulated boom or slave member 11 including an upper arm element 12 and a lower arm element 13. A control or master member 15 including an upper arm element 16 and a lower arm element 17 is also provided. One end of the upper arm element 12 of the slave member is pivotally connected to a stanchion or slave support member 20 about a horizontal axis 21 to form a shoulder joint. The slave support member 20 is supported in the bearing member 22 which is connected to a base or mount member 23. The support member 20 is pivotal on mount member 23 about a vertical axis 24 thereof. The other end of the upper arm element 12 is pivotally connected to one end of the lower arm element 13 to form an elbow joint and is pivotal about a second horizontal axis 14. The other end of the lower arm element 13 has connected thereto end-effector-positioning apparatus 25 and an end effector 26. The endeffector-positioning apparatus 25 comprises three rotary elements 27, 28 and 29, connected in series so as to permit movement of the end effector 26 about any one of three mutually perpendicular axes. The end effector 26 shown is one in which suction cups 31-34 are provided for interfacing and securing thereto objects to be moved by the manipulator.

The upper arm element 16 of the master control member is pivotally connected to a master support member 40 and is pivotal about a third horizontal axis 41. The master support member 40 in turn is pivotally mounted to the slave support member 20 and is displaced horizontally therefrom so as to be pivotal with respect-thereto about a second vertical axis 42. The other end of the upper arm element 16 is pivotally connected to one end of the lower arm element 17 and pivotal about a fourth horizontal axis 43. A handle 45 is provided on the other end of the lower master arm element 17. The handle 45 is provided with buttons, switches and the like responsive to finger action to effect through appropriate electrical and hydraulic control elements the operation of the end-effectorpositioning effector elements 27-29 and the end effector 26. Also connected to the slave support member 20 and displaced horizontally from the slave support member so that the control member 15 is positioned between an operator of the manipulator apparatus and the slave member is a platform or operator support member 50 shown in the form of a seat for the operator and a foot rest so that the operator is oriented in the direction in which the end of the slave member 11 is oriented and the operator moves in azimuth so as to maintain such orientation. The control arm member 15 is provided with elements 16 and 17 which are comparable in length with the corresponding portions of the adjacent arm of an operator so that motions of the arm of the operator when grasping the handle produces motions in the elements of the control member 15 which correspond to the motions of the arm of the operator. Also, the ratio of the length of the lower arm element of the master member to the length of the lower arm element of the slave member is made substantially equal to the ratio of the length of the upper arm element of the master member to the length of the lower arm element of the slave member to provide a good sense of position correspondence between handle 45 and end effector 26. Hydraulic actuators, control valves, and control linkages are interconnected with the slave member 11 and the control member 15 in a manner which will be fully described in connection with FIGS. 2 and 3 so that as an operator moves the handle 45 of the control member 15, the elements of the slave member 11 mimic the motion of the elements of the control member 15. Accordingly, the position of the hand of the operator produces a corresponding position of the end effector 26 and, in addition, force exerted by the end effector on an object is reflected back to the handle 45 reduced in magnitude so that the operator has a feel for the force being applied by the slave member.

Reference is now made to FIG. 2 in which elements corresponding to the elements of FIG. 1 are denoted by the same reference symbol. The slave support member is a stanchion generally U-shaped to the base of which is connected to a vertically extending shaft 51 which extends vertically downward and is supported in the manipulator mount member 23 by bearing 22 and a thrust bearing (not shown) located below the member 20. To the lower end of the shaft 51 is connected a sprocket 52 the teeth of which are engaged by a chain 53. One end of the chain 53 is connected to the piston of a hydraulic actuator 54 and the other end thereof is connected to the piston of another hydraulic actuator 55. The cylinders of the actuators 54 and 55 are secured to the support 23. Accordingly, by appropriate energization of the actuators with hydraulic fluid the slave support member 20 can be made to move about the first vertical axis 24. Bearing surfaces are provided in the opposed regions of the legs of the slave support member 20 and journals are provided in one end of the upper slave arm element 12 for enabling movement of the upper arm element about the horizontal axis 21. The upper arm element may be a structural element rectangular in cross section or of other coluinnar design to provide the desired strength thereto. in this figure the element 12 is shown open for the purposes of illustrating the embodiment of the invention. To the other end of the upper arm element 12 is pivotally connected one end of the bearing elements located in lower arm element 13 by means of the elements 12 and 13. The lower arm element is pivoted about the second horizontal axis 14 with respect to the upper arm element. The upper arm element and the lower arm element have longitudinal axes which intersect and lie in a vertical plane which is perpendicular to the aforementioned first horizontal axis 21 and the second horizontal axis 14.

The master control member 15 includes an upper arm element 16 and a lower arm element 17. One end of the upper arm element 16 is connected to master support member 40 and is pivotal with respect thereto about a third horizontal axis 41. Master support member 40 is connected to a slave support extension member 56 so as to be pivotal about the second vertical axis 42 to a limited extent. The second vertical axis 42 is horizontally displaced along extension member 56 from the first vertical axis 24. The first vertical axis 24, the first horizontal axis 21 and the second vertical axis 42 lie in a vertical plane. The other end of said upper arm element 16 is pivotally connected to one end of the lower arm element 17 of bearing elements by means located in elements 16 and 17 and is pivotal about a fourth horizontal axis 43. The other end of the lower arm element 17 has secured thereto a handle 45 for manipulation of the control member 15. The longitudinal axes of the upper arm element 16 and the lower arm element 17, respectively, intersect and lie in a second vertical plane perpendicular to the aforementioned third horizontal axis 41 and fourth horizontal axis 43 and intersecting the aforementioned vertical plane including the first and second vertical axes.

A first linkage means 60 is provided for transferring angular displacement of the lower master arm element 17 with respect to the upper master arm element 16 about the fourth horizontal axis 43 to a corresponding angular displacement of a first reference arm element 61 about the first horizontal axis 21 pivotally supported in the sidewalls of the master support member 40, and which pivotally supports upper ann element 16, a lever arm 64 at one end pivotally connected to an intermediate point on the lower arm element 17 and at the other end pivotally connected to a side of the sprocket 62. Accordingly, movement of the lower ann element 17 about the upper arm element 16 causes a corresponding movement of the sprocket 62. The angular displacement of the sprocket 62 about the third horizontal axis 41 which is coincident with the axis of the shaft 63 is transferred to angular displacement about the first horizontal axis 21 by means of another sprocket 65 fixedly mounted to one end of tubular member 66 having its longitudinal axis coincident with the first horizontal axis 21 and rotatable thereabout. The tubular member 66 is rotatably supported in the tubular slave support extension member 56.

. An endless chain 67 with a small amount of slack engages the teeth of the sprockets 62 and 65 and interconnects them. The reference arm element 61 is connected to the other end of the tubular member 66. Accordingly, the movement of the sprocket 62 about the third horizontal axis is transferred through the second sprocket 65 and through the tubular member 66 is transferred to the tab 61 to produce a rotation of the longitudinal axis thereof about the first horizontal axis 21.

Second linkage means 70 are provided for transferring angular displacements of the upper master arm element 16 with respect to the third horizontal axis 41 to a corresponding an gular displacement of a second reference arm element 17 about the first horizontal axis 21 and includes a second lever arm 72 which at one end is universally pivotal about a shaft 73 rigidly connected to a point on the upper master arm element 16 and at the other end is universally pivotal about a shaft 74 rigidly connected to an offset 75 member rigidly mounted on shaft 76. Shaft 76 has an axis of rotation coincident with the first horizontal axis 21. The shaft 76 is rotatably supported within extension member 56 and connects to reference arm 71 at the other end thereof. The socket 78 is provided at one end of lever arm 72 which engages a ball 79 fixedly secured to shaft to provide a universal joint. Similarly, a socket 80 is provided at the other end of lever arm 72 which engages a ball 81 fixedly secured to shaft 73 to provide another universal joint. Enough play is provided in the aforementioned universal joints so that small angular displacements, for example less than 10, of the support member 40 about axis 42 with respect to extension member 56 on which member 40 is pivotally mounted does not bind the universal joints yet allows the indicated displacements to take place. Accordingly, movement of the upper master arm element 16 about the third horizontal axis 41 causes a movement of the shaft 76 about the first horizontal axis 21 which in turn causes the second reference arm 71 to execute a corresponding movement about the first horizontal axis.

A system of levers is provided responsive to the orientation of the longitudinal axis of the first reference arm 61 to the orientation of the longitudinal axis of the lower slave arm element 13 to produce a displacement in a differential lever arm 85. The direction of such displacement of the lever arm 85 from a neutral position and the magnitude of such displacement corresponds to the direction and magnitude of misalignment of the lower slave arm element 13 and the lower master arm element 17. To this end a lever 86 is provided connected between the remote end of the first reference arm 61 and one end of the differential lever arm 85. Another lever 87 is provided connected between an extension of the lower slave arm beyond the horizontal pivotal axis 14 thereof and the other end of the differential lever arm 85. An intermediate point 88 on the differential lever arm 85 is connected to one end of an actuating arm 89, the other end of which is pivotally secured to the upper slave arm element 12. The longitudinal axis of the first reference arm 61 is aligned to correspond with the longitudinal axis of the lower master arm element 17. Accordingly, a movement of the lower master arm element proand includes a sprocket 62 mounted to a shaft 63 which is 75 vides a corresponding angular displacement of the reference arm which produces a movement in one direction of the differential arm 85. if the other end of the differential arm is maintained fixed the movement of the differential arm is in the same direction. To maintain the actuating arm 89 fixed in position, it is necessary to move the other end of the differential arm 85. Accordingly, the magnitude and direction of the movement of the actuating arm 89 corresponds to the magnitude and direction of movement of the longitudinal axis of the lower master arm 17. Such movement is sensed by a control valve 90 connected to the upper slave ann element 12. The control valve has a button which is moved in one direction or the other from a neutral position to cause fluid to flow from one side to the other or vice versa of a slave hydraulic linear actuator 91 connected between the upper slave arm element 12 and the lower slave arm element 13. The control system is polarized so that the flow of fluid causes the actuator 91 to bring the lower slave arm 13 into correspondence with the lower master control arm 17. Such action causes the differential lever arm to be moved so as to maintain the actuating arm 89 in a neutral position.

A second servo loop means is provided responsive to the displacement of the second reference arm 71 to maintain alignment of the longitudinal axis of the upper slave arm element 12 with the longitudinal axis of the upper master arm element 16. Connected to the upper slave arm element 12 is another control valve 92 having a button 93 which bears against the second reference arm 71. Movement of the reference arm 71 in one direction or the other corresponding to movement of the upper control arm 16 in one direction or the other about the third horizontal axis 41 causes a displacement of the button 93 inward or outward, and accordingly directs hydraulic fluid to flow in one direction between the ends of the linear actuator 94 or in the other direction to cause the slave arm element 12 to move in one direction or the other to maintain correspondence in the direction of the longitudinal axis thereof with respect to the longitudinal axis of the upper control arm element 16.

A third servo loop means is provided responsive to the displacement of the second vertical plane, that is the plane of the longitudinal axes of the elements 16 and 17 of the control member about the second vertical axis 42 from a position in which it is parallel to the first vertical plane, that is the plane including the longitudinal axes of the elements 12 and 13 of the slave arm member 11, for maintaining the planes in parallel. To this end the slave support extension member 56, one end of which is secured to the stanchion is provided at the other end thereof with a U-shaped member 95, the base 96 of which is attached to the tubular member 56. A pair of bearing elements are provided, one in each of legs 97 and 98 of the U- shaped member 95 in opposed relationship and aligned along the second vertical axis 42. The bearing element associated with leg 97 includes a shaft 99 secured to the leg 97. To the upper end of the shaft 99 is secured a cam 100 having a peripheral surface 101 which is eccentric with respect to the second vertical axis 42. A bracket 102 having an upper horizontal portion 103, a lower horizontal portion 104 and a side portion 105 is connected between opposed walls of the support 40. The upper horizontal portion 103 is connected to the wall of the support 40 adjacent the slave member 11, the side portion 105 is connected to the opposed wall of the support 40 and the lower horizontal portion 104 is provided with a hearing which engages a journal in leg 98 of the U-shaped member 95. As mentioned above, a bearing element is provided in the upper horizontal portion 103 so as to permit pivoting of the support 40 with respect to member 95 about the second vertical axis 42. A servo valve 106 having an actuating button 107 is mounted to a wall of the support 40. The button 107 bears against the peripheral surface 101 of the cam 100. When the aforementioned second vertical plane is aligned with the aforementioned first vertical plane, the button 107 of valve 106 is in a neutral position on the cam 100. When the control arm member 15 is moved in one azimuth direction, the support 40 is displaced about the vertical axis 42 in one direction and the cam displaces the button in one direction to produce a flow of hydraulic fluid through the actuators 54 and 55 to cause the shaft 51 to move in a direction to align the first vertical plane with a second vertical plane. Conversely, when the control arm member 15 is moved in the opposite azimuth direction the earn displaces the button 107 in the opposite direction from neutral to cause actuators 54 and 55 to move shaft 51 in the opposite direction to align the first and second vertical planes. The movements of the control arm member 15 in one direction or the other about the second vertical axis 42 need not be large, i.e., less than a degree, since it need be sufficient only to produce sufficient error signal in the servo loop to cause the slave arm member 11 to move in correspondence therewith. The provision of a chain 67 linking the first sprocket 62 and second sprocket 65 which is slightly slack enables such limited movement to be performed without binding the mechanism. Similarly, the lever arm 72 having ball and socket joints on the ends thereof with a small tolerance is provided to avoid binding of the lever arm yet permitting the error signal in the servo loop to be produced.

Limit switches 110 and 111 are provided responsive respectively to engagement of cams 112 and 113, therewith in the azimuth limit positions of the support member 20 to block flow of fluid to the actuators 54 and 55 and thereby limit the azimuth excursion of the support member 20 to those limits. The circuit connections and operation of the limit switches 110 and 111 will be further described in connection with FIG. 3.

Force feedback is applied to the handle 45 by means of linear actuators 114, and 116. The linear actuator 114 pivotally is connected between the elements 16 and 17 to provide torque about the fourth horizontal axis 43. The linear actuator 115 is pivotally connected between element 16 and master support member 40 to provide torque on the third horizontal axis 41. The linear actuator 116 is pivotally connected between members 40 and 95 to provide a torque about the second vertical axis 42. As mentioned above, actuator 91 is connected between elements 12 and 13 and is used for applying torque about the second horizontal axis 14. Actuator 94 is connected between element 12 and member 20 and is used for applying a torque about the first horizontal axis 21. The actuators 54 and 55 are connected to a chain 53 which moves the element 20 about the first vertical axis 24.

Each of the slave actuators 91, 94 and 54, and 55, and also each of master actuators 114, 115 and 116 is in an assembly of a cylinder with a piston therein and has a pair of fluid ports, one at each end of the cylinder. The application of a pressure differential between one side and the other side of the piston produces a net force thereon. The magnitude of such force and the direction of such force being dependent upon the magnitude and direction of pressure differential and, of course, on the active cross-sectional area of the piston. The active area of each of the pistons of actuators 114, 115 and 116 is substantially smaller by a predetermined ratio than the active area of each of the pistons of actuators 91, 94, 54 and 55. The pressure differential applied to each of actuators 114, 115 and 116 is substantially the same as appearing across respective actuators 91, 91 and one of the pair of actuators 54 and 55. The actuators 114, 115 and 116 are mechanically connected to provide torque lever arms about horizontal axes 43, 41 and vertical axis 42, respectively which are substantially smaller than lever arms provided to actuators 91, 94 and one of a pair of actuators 54 and 55, respectively. Each of the actuators 114, 115 and 116 are situated in respect to the corresponding actuator or pair of actuators on the slave member in a kinematically similar position so that the ratio of slave torque to master torque for a pair of corresponding horizontal axes is the same for any location of the handle 45. Preferably such ratio is made the same for each of the three sets of axes so that force fed back to the handle is a faithful replica of the force encountered by the end effector 26. Also, of course, actuators 114, 115 and 116 are connected in circuit so that pressure differential existing thereacross is opposite in direction to the pressure differential existing at actuators 91, 94 and at pair of actuators 54 and 52, respectively, to provide a restraining force to the movement of the handle 45 which produced the force in the slave member.

The magnitude and direction of pressure applied to each of the actuators 91, 94, and 54 and 55 is controlled by a hydromechanical servo valves 90, 92 and 106. As mentioned above, servo valve 90 controls the pressure applied to actuator 91, valve 92 controls the pressure applied to actuator 94 and valve 106 controls the pressure applied to actuators 54 and $5.

The structure of each of the control valves 90, 92 and 106 and the manner of their connection to respective slave actuators 91, 94 and a pair of linear actuators 54, 55 as well as the operation thereof will be explained in detail in connection with FIG. 3. Also in connection with FIG. 3, the manner of applying pressure differential appearing across each of the slave linear actuators 91, 92 and the azimuth set 54 and 55 to the force feedback linear actuators 114, 115 and 116, respective ly, will also be described.

Reference is now made to FIG. 3 in which elements identical with the elements of FIG. 2 are denoted by the same reference symbols. Specifically, in this figure are shown mechanical servo valves 92, 90 and 106 for controlling fluid flow to respective linear actuators 91, 94 and pairs of linear actuators 54 and 55. Each of the servo valves 92, 90 and 106 is a four-way proportional control pressure flow valve to which a mechanical input on a button thereof produces a flow at a pair of output ports P, and P the magnitude and direction of which is proportional to the magnitude and direction of movement of the button about a neutral position. In addition to the output ports P and P each of the valves is provided with a source port S for the application of fluid pressure from a reservoir or a pressure generator and a return port R therefor. Each of the control valves is a valve such as a type 50-346 hydromechanical servo valve manufactured by Moog Inc. of Proner Airport, East Aurora, New York.

As mentioned above, each of the linear actuators 91, 94 and 54 and 55 include a cylinder and a piston movable therein. The cylinder is provided with a port at one end and another port at the other end thereof. The application of a pressure differential between the ports of the cylinder provides a force between the piston and cylinder thereof. Coupling members are connected to the piston and the cylinder which in turn are connected to appropriate elements between which it is desired to apply the force. As shown in this figure, the linear actuator 94 is connected between elements 12 and 20. Linear actuator 91 is connected between elements 12 and 13. The piston of linear actuator 54 is connected to one end of chain 53, the other end of which is connected to the piston of actuator 55.

The hydraulic fluid source line 118 of a source of pressurized hydraulic fluid is connected to each of the source ports of the valves 92, 90 and 106 and the return ports of each of the control valves 92, 90 and 106 are connected to the return line 119 of the hydraulic fluid source. The output ports P and P of control valve 92 are connected over lines 120 and 121, respectively, to respective ports on the linear actuator 94. Line 120 includes fluid pathway of a two-way directional con trol valve 122 which is open when electrically energized and closed when deenergized. The valve 122 provides a means to lock the actuator 94 in the event of electric power failure. The output ports of the valve 90 each are connected to respective ports of the linear actuator 91 along lines 124 and 125. Line 124 includes another fluid pathway of valve 122 which is open when energized and closed when deenergized. Valve 122 also provides a means to lock actuators 91 as well as 94 in the event of power failure. Each of the output ports P, and P of valve 106 is connected to a respective port linear actuator the ports at the same end of the linear actuators 54 and 55 over lines 126 and 127. The other ports of the linear actuators 54 and 55 are connected together and are connected to the return line 119 of the fluid source. A lock valve 128 is connected in line 126 to block fluid flow therein when electrically deenergized by limit switch electrically connected thereto. Similarly, lock valve 129 is connected in line 127 to block fluid flow therein when electricity deenergized by limit switch 111 electrically connected thereto.

Force feedback to the elements 16 and 17 are provided by linear actuators and 114 which as mentioned are connected between elements 16 and 40 and 16 and 17, respectively. While the pressure difference appearing across the slave actuator 94 and the slave actuator 91 could be applied respectively to the linear actuators 115 and 114, because of the large difference in masses of the master and slave circuits instabilities are produced in such circuits. Accordingly, in order to stabilize the master loop, isolation is provided which makes the master control circuit relatively independent of the slave circuit. The isolation is achieved by actuator 94 and actuator 115, a pair of pressure sensors 130 and 131, a differential amplifier 132 and a control valve 133 and similarly for actuator 91 and actuator 114 providing a pair of pressure sensors 135 and 136, a differential amplifier 137 and a control valve 138.

Each of the valves 133 and 138 are electrohydraulic flow valves having a source port S and a return port P and a pair of output ports P, and P The valve is provided with solenoids responsive to current applied thereto to control the flow in the valve. Input current flow into one solenoid produces a flow in one direction between the output ports P and P,, the magnitude of which depends upon the magnitude of the current. Similarly, input current flow to the other solenoid produces a fluid flow in the opposite direction between the output ports P and P,, the magnitude of which is dependent upon the magnitude of such current flow. The electrohydraulic flow valve is of a type such as type 30 Flow Control Serve Valve made by Moog Inc., Proner Airport, East Aurora, New York. Each of the pressure transducers 130, 131, 135 and 136 are transducers of the strain gauge type and have a pair of fluid pressure input ports and a pair of electrical output terminals from which a voltage is derived proportional to the pressure differential applied between the input ports. The magnitude and the direction of the voltage is dependent upon the magnitude and direction of the pressure applied between input ports of the strain gauge. The pressure transducers or sensors such as Model 620-1 manufactured by Standard Controls Inc., South Bayview St., Seattle, Washington, may be used. Each of the differential amplifiers 132 and 137 has a pair of input channels and a pair of output channels. The amplifier compares the signals applied to the input channels and develops an output current in one channel or the other depending on which of the two signals is larger. The magnitude of the output current depends on the magnitude of the difference. The pressure input ports of pressure sensor 130 are connected to the ports of the actuators 94. The pressure input ports of pressure sensor 131 are connected to the ports of actuator 115. The electrical outputs of sensors 130 and 131 are applied to respective input channels of the amplifier 132. Each of the output channels of the amplifier 132 are applied to a respective solenoid of the control valve assembly 133. Each of the output ports P, and P of control valve assembly 133 are applied to a respective port of actuator 115. Accordingly, when the pressure differential between the ends of the actuator 94 and the actuator 1 15 are the same, the outputs from the transducers 130 and 131 are the same and no net output would be produced from the amplifier 132, consequently no fluid flow would appear at the output ports P, and P 2 of the valve assembly 133. Should the linear actuator 94 be energized by fluid flow or pressure differential appear between the ends thereof, a signal would be produced in transducer 130 which would produce a net output from the amplifier 132 and would accordingly actuate valve assembly 133 to apply fluid pressure to the linear actuator 115 to develop an output from the transducer 131 and accordingly restore balance to the system. The elements of the feedback loop are phased in a manner to produce such restoration.

Similarly, the pressure input ports of pressure sensor 135 are connected to the ports of the actuator 91. The pressure input ports of sensor 136 are connected to the ports of actuator 114. The electrical outputs of sensors 135 and 136 are applied to respective input channels of the amplifier 137. Each of the output channels of the amplifier 137 are applied to a respective solenoid of the control valve assembly 138. Each of the output ports P, and P of the control valve 138 is connected to a respective port of actuator 114. The circuits described are so phased that the pressure ditferential appear across the ends of the actuator 91 are essentially matched by a pressure differential across actuator 114 in the manner described above in connection with actuators 94 and 115. The linear actuator 116 for azimuth force feedback has a cylinder thereof connected to the element 40 and the piston connected to the element 95. One port of actuator 116 is connected to a port of the actuator 54 and the other port thereof is connected to a port of the actuator 55, each through respective orifices 140 and 141. The fluid circuit connections are made so that actuator provides a force to member 40 counter to the movement thereof which produced movement of member 95. The actuator 116 not only provides force feedback but also acts in conjunction with the orifices 140 and 141 as a dashpot to stabilize the operation of the master azimuth circuit. The stabilizing circuit is described and claimed in a copending patent application filed Apr. 30, 1970, Ser. No. 33,l9l and assigned to the assignee of the present invention.

Reference is now made again to FIGS. 1 and 2 in which is shown a plurality of rotary actuators 27, 28 and 29. Each of the actuators has a stator and a rotor. Each of the actuators is fluid operated. The rotor of actuator 27 is connected to the end of the member 13 and the stator of actuator 27 is connected to the rotor of actuator 28. The stator of actuator 28 is connected to the stator of actuator 29, the rotor of which is connected to the end effector 26. A plurality of finger operated switches 145, 146 and 147 are provided on the handle 45. Movement of the switch 145 to the left or right causes electrical and hydraulic circuits to be actuated to move the end effector 26 to be moved in yaw by actuator 28 to the left or right. Moving the switch 145 forward or reverse causes electrical and hydraulic circuits to be energized to actuate the rotary actuator 27 to move the end effector 26 up and down in pitch. Actuation of the trigger switch 146 causes electrical and hydraulic circuits to energize the rotary actuator 29 to rotate the end effector 26. Each of the rotary actuators 27, 28 and 29 are rate actuators in that upon the application of fluid the rotor thereof moves with respect to the stator until energization is removed or until appropriate stops are reached for each of the actuators which limit the movement of the rotors with respect to the stator thereof. The base of the cups 31, 32, 33 and 34 are provided with openings each of which are sealed by a cover. The cover is mechanically opened upon the interfacing of the cups with a surface of the object to be moved thereby by vacuum forces secure the object to the end effector. The switch 147 provides a means for releasing vacuum and hence breaking the seal between the end effector and the object to be moved.

in operation of the manipulator apparatus of FIGS. 1, 2 and 3, the operator would initially set on the seat of support member 50 and grasp handle 45 on the master control member. Upon energization of the hydraulic and electrical circuits of the system to free the slave elements from a stowed position, the apparatus would be ready for operation. Movement of the handle 45 in an arbitrary direction in space would produce a corresponding movement of the end of the element 13 and the end effector 26 into a corresponding position. Such operation would be produced by the servoing action described above. If such arbitrary movement of hand 45 required that element 17 be moved with respect to 16, tab 61 would be moved to produce a corresponding movement in the arm 89 which would actuate the control valve 90 in appropriate direction to energize linear actuator 91 to bring the element 13 into correspondence with the orientation of element 17.

Similarly, if such arbitrary movement of the handle 45 required that element 16 be moved about its horizontal axis 41, the control valve 92 would produce a fluid flow into linear actuator 94 to cause the spatial orientation of element 16 to line up with the element 12. Similarly, if such arbitrary movement of handle 45 required that support member 40 be moved in azimuth direction with respect to the horizontal axis 42, the servo valve 106 would be actuated to actuate the linear actuators 54 and 55 in the appropriate direction to cause the slave support member 20 to move in azimuth in correspondence with the movement of the control handle. lf now the handle 45 is moved so as to cause the end effector 26 to abut an object, force applied to the object is reflected back to the handle 45 reduced in magnitude by a predetermined ratio as described above by virtue of the fact that force feedback cylinders 1 14, 115, and 116 are connected between elements 17 and 16, between elements 16 and 40. and elements 40 and 95, respectively. Accordingly, the operator has a sense of feel for the amount of force that his movement of the handle produced. If it is desired now to life an object, such is accomplished by means of the end efiector 26. The handle now can be retracted to position the object.

Reference is now made to FIGS. 4, 5, 6, and 7 in connection with which the invention of the present application will be particularly described. FIG. 4 is similar to FIG. 2 and the elements of FIG. 4 are identical to the elements of FIG. 2 are designated by the same symbols. The master support member 40 of FIG. 4 is identical to the master support member 40 of FIG. 2, and also the control member 15 is identical to the control member 15 of FIG. 2. The endless chain 67 of FIG. 4 has been eliminated from FIG. 4 for reasons of clarity of showing the assembly of the present invention.

The spring counterbalance assembly applied to the upper control arm element includes a lever arm 151 provided by the extension of the control arm element 16 beyond the axis of rotation thereof about the third horizontal axis 41. A support pin 152 is provided in the end thereof remote from the third horizontal axis 41. The assembly 150 also includes a bearing support member 153 in the form of a sprocket of small radius rotatable about a shift 154 extending horizontally between the side portions of the member 40. The shaft 154 is placed below the third horizontal axis 41 and on the side thereof away from the side from which the control member 15 extends. A flexible tension member 155 in the form of a chain and a coil spring member 156 are also provided. One end of the tension member 155 is connected to the pin 152 attached to the upper arm element extension 151 and the other end of the tension member 155 is connected to one end of the spring member 156. The other end of the spring member 156 is connected to a crossbar 157 through an adjusting bolt 162 for adjusting spring tension. The crossbar 157 is connected between the sidewalls of the master support member 40. An intermediate portion of the tension member 155 bears on a first support point 158 (clearly shown in FIG. 6) of the first bearing member 153 on a side thereof which is remote from a third horizontal axis 41. Another sprocket 160 is also provided below sprocket 153 to enable securing of the fixed end of the spring member 156 to the crossbar 157. The idler sprocket 160 is supported on a shaft 161 extending between the sidewalls of the master support member 40. Rotation of the upper arm element 16 in the hearing about the horizontal axis 41 causes the spring member 156 to be deflected and exert a counterbalancing force on the upper arm element 16. The geometrical and physical proportioning of the elements of the upper arm element counterbalance assembly will be fully described in connection with FIGS. 5 and 6.

Spring counterbalance assembly for the lower control arm element 17 is similar to the counterbalance assembly for the upper control arm element 16. The assembly for the lower control arm element includes a tab 171 providing a lever arm, one end of which is secured to the shaft 63 and hence is rotatable about the third horizontal axis 41 and the other end is provided with support aperture 172 for fastening another tension member 173 thereto. The assembly also includes bearing support member 174 and spring member 175. The bearing member 174 is also in the form of a sprocket of small radius, free to move about the shaft 154. One end of the spring member 175 is adjustably attached to the crossmember by means of nut and bolt assembly 176 and the other end extends downward. The tension member 173 in the form of a chain, has one end secured to aperture 172 in arm 171 and has the other end secured to the downward extending end of the spring member 175. An intermediate portion of the tension member 176 bears on the sprocket 174 on a support point 177 thereof which is on a side remote from the side of the third horizontal axis 41. A second idler sprocket 1 78 is provided on the shaft 161 to enable the spring member 175 to be secured as shown, that is with an adjustable positioned end up and the other end down. The geometrical arrangement and the physical characteristics of the elements of the spring counterbalance assemblies will be described and explained in greater detail in connection with FIGS. 5, 6, and 7 to which reference is now made.

FIG. includes two line diagrams, one for the control member and the other for the controlled or slave member 11 of FIG. 1 in which corresponding elements are denoted by the same numerical designation. FIG. 5 shows the forces acting on elements 16 and 17 of the control arm member 15 and also on the elements of the slave member 11 and the point of application thereof. As described in connection with FIGS. 1, 2, and 3 means are provided so that movement of the control arm member 15 causes the elements of the slave member 11 to move in a way to be identically oriented with the corresponding control member elements. Also force feedback loops are provided from the slave elements to the master elements to provide an operator of the control member with a sense of feel for the force being applied by the slave member. In the absence of any work being done or force being applied by the slave member, the unloaded or dead weight of the elements of the slave member produce a corresponding force on the elements of the controlled member. Accordingly, an operator in operating the manipulator has to apply force to overcome not only the weight of the control arm elements but also to overcome the unloaded or dead weight of the slave arm elements as reflected back to the control arm elements. Such force or exertion required by the operator considerably limits the ease and freedom with which he can manually direct the slave member to perform the functions which he desires it to perform. Also the need for the operator to counterbalance by his effort the unloaded weight of the elements of the manipulator distorts the sense of fee] of the force being applied by the slave member.

The torque produced on the lower control arm element about the elbow joint E is given by the following equation:

TEMX[FME.R represented z( l/R)(FSE.RSE) ]cos a (l) The torque produced about the shoulder joint 5 on the upper control arm element is represented by the following equation:

TSM X Torque produced by dead weight of master upper arm 70 element and master lower arm attached thereto, and slave upper arm element and slave lower arm element attached thereto as reflected to upper master arm element RME x Distance from elbow pivot E to center of gravity of lower master arm R' Length of upper master arm element R:SS x Length of upper slave arm element FMS X Weight of upper master arm RMS x Distance from shoulder pivot point S to center of gravity of upper master arm element FSS x Weight of upper slave arm RSS x Distance from shoulder pivot point S to center of gravity of upper slave arm element 4 k x Angle of longitudinal axis of upper master arm element with respect to a horizontal plane P Reference is now made to FIG. 6 which shows the line diagram of the spring counterbalance assembly as applied to the control member 15 of FIG. 4. In this figure elements identical to elements of FIG. 4 are designated by the same reference numerals. The upper arm element 16 is pivotably about the third horizontal axis 41 and makes an angle P with a vertical line extending vertically upward from the third horizontal axis. FIG. 6 is a representation of the movement occurring in a plane perpendicular to the third horizontal axis 41 and will be used for deriving the relationship between certain geometrical and physical quantities achieving counterbalancing. The general matter of spring balancing of loads is described in an article entitled "Spring Mechanisms" by Kurt Hahn in Product Engineering of Jan. 9, I961. The following is an extension of the principles described therein. Nomenclature to be used in the derivation is as follows:

F x Force or load to be balanced n x Effective length of force lever arm M x Fn x Torque produced by an equivalent beam in a horizontal position r x Spring moment arm a x Straight line spacing between pivot point or axis 41 and tangential point 158 on bearing member 153 B: x Angular displacement of element 16 with respect to a vertical line from axis 41 B x Angular displacement of r with respect to straight line a P x Spring force h x Projection of spring moment arm r onto a line normal to direction of application of spring force P d x Distance between end of spring moment arm r to tangent point 158 on bearing member 153 c xP/d x Spring rate or constant As torque produced by force F about axis 41 is equal to 'torque produced by spring force P,

Fpsin I '=Ph (3) Since rsin B=dlsin 3, and sin Accordingly, it is seen from equation (5) that when the angle 1 is equal to the angle '1 and the spring force F is made a function of the distance 11, complete counterbalancing over the range of movement of the upper element 16 may be achieved by use of a spring having the spring constant or rate set forth in equation (7). The reflected torque from the slave upper arm element is counterbalanced as well. It should be ob served that in the unstressed position and the tension member 155 disconnected from pin 152, the disconnected end extends to the support point 158. With this requirement met, attachment of the tension member 155 to the lever arm 151 or r ideally should provide perfect balance for the upper arm element 16. In view of the physical dimensions of the tension member and the finite size of support points, friction factors and the like, the derivation does not produce a perfect balance but does provide a balance sufficiently close for all practical purposes to provide counterbalancing. It should be noted in connected with FIG. 4 that for fine adjustment to accommodate changes, such as changes in the constants of the slave element end effectors and torque feedback ratios from lower to master elements, that the spring constant may be varied by linking a fewer number of turns of the spring member. Bolt and nut assembly 162 provides for adjusting the position of the remote end of the tension member to coincide with point 158 when the spring member is free of stress so that the relationship P=d is established. Also, while a spring member which provides a force when it is deflected in tension has been shown it will be appreciated that a spring which provides a force under compression may also be used. It should be noted that angles 4 and d are less than 180 and the angle d is the angle between the normal from the remote end of the lever arm r to the third horizontal axis and the normal from the first support point 158 to the third horizontal axis.

Reference is now made to FIG. 7 which shows a line diagram of the lower arm element 17 and the counterbalance spring assembly 170 as applied thereto. In this figure .elements identical with the elements of FIG. 4 are designated by the same symbol. In this figure, the lower control arm element 17 is pivotable about the fourth horizontal axis 43 and the longitudinal axis of the lower arm element makes an angle l with a vertical line extending upward from the fourth horizontal axis. A pantograph assembly including a lever 64 at one end pivotally connected to the lower control arm element 17 and at the other end pivotally connected to a point on sprocket 62 which is rotatable about the third horizontal axis 41. The lever arm 64 is proportioned and so connected that a given angular displacement of the lower arm element 17 about the fourth horizontal axis 43 produces a corresponding angular displacement of the sprocket 62 about the third horizontal axis 41. Connected to the sprocket 62 is a second lever arm 171 having a pair of ends, one end of which is connected to the shaft 63 and has an axis coincidental with the third horizontal axis 41 and the other end is pivotal about the third horizontal axis 41. The pantograph arrangement described provides a means for transferring an angular displacement of the lower arm element 17 with respect to theupper master arm element about the fourth horizontal axis 43 to an equal angular displacement of the lever arm 171 about the third horizontal axis 41. The angle between the normal from the remote end of the lever arm 171 to the third horizontal axis 41 and the normal from the second support point 177 to the third horizontal axis 41 is designated 1 and is made equal to the angle 1 Both of these angles are less than 180. The other symbols in the diagram of FIG. 7 are the same as the symbols in the diagram of FIG. 6 and identical analysis is applied to derive the formula for the spring constant of the spring 175. As in the case of the assembly of FIG. 6, using a spring constant c resulting from the derivation for the lower control arm element and using a length for the tension member 173 such that when the spring 175 is in an unstressed position the tension member 173 extends to the second support point 177, attachment of the tension member 173 to the remote end of the lever arm 171 or r provides a balance for all positions of the lower control ann element about the third horizontal axis and as well for movements of the lower control arm element about the third horizontal axis resulting from movement of the upper control arm element. In addition, the reflected torque from the slave lower ann element is counterbalanced. The same spring constant adjustment and tension member zero spring force position adjustment capability is provided in the counterbalance assembly 170 as in counterbalance assembly 150 by means of nut and bolt assembly 176.

It should be noted that in addition to counterbalancing the master and slave members of the manipulator, the spring members 156 and 175 also provide dynamic stabilization of the elements (i.e., inhibit oscillation thereof) of the master member.

While we have shown a particular embodiment. it will of course be understood that we do not wish to be limited thereto since many modifications may be made in the arrangement shown and in the instrumentalities employed. We contemplate by the appended claims to cover any such modifications as fall within the true spirit and scope of our invention.

What we claim as new and desire to secure by Letters Patent of the United States is:

1. In combination,

a slave support member,

a slave member, one end of said slave member pivotally connected to said slave support member and pivotal about one horizontal axis,

a master support member,

a master member, one end of said master member connected to said master support member and pivotable about another horizontal axis,

a servo loop means responsive to displacements of said master member to maintain alignment of the longitudinal axis of said slave member with the longitudinal axis of said master member,

a force feedback means responsive to torque of said slave member about said one horizontal axis for applying a corresponding torque reduced in magnitude to said master member about said other horizontal axis in a direction in opposition to the direction of movement of said master member producing the torque in said slave member,

a lever arm member having a pair of ends, one end of which is in fixed relationship to said master member and movable about said other horizontal axis therewith,

a bearing member,

a flexible tension member,

a spring member,

one end of said flexible tension member connected to said other end of said lever arm member and the other end of said tension member connected to one end of said spring member, the other end of said spring member connected to said master support member,

an intermediate portion of said tension member bearing on a support point of said bearing member on a side thereof remote from said other horizontal axis,

the angle less than formed between a line extending from said other end of said lever arm member to said third horizontal axis and a line extending from said support point to said third horizontal axis being equal to the angle less than 180 between the longitudinal axis of said master member and an axis extending vertically upward from said third horizontal axis,

the spring constant of said spring member being equal to M/ar, where M is the moment of said master member, and the moment of said slave member as reflected to said master member,

a is the length of the line from said support point to said third horizontal axis, and

r is the length of the line from said other end of said lever arm to said third horizontal axis.

2. The combination of claim 1 in which the length of said tension member being such that the end thereof remote from the end connected to said spring member when unattached and said spring member is in its unstressed condition extends to said support point.

3. In combination,

a slave support member,

a slave member including an upper arm element and a lower arm element, one end of said upper arm element pivotally connected to Said slave support member and pivotal about a first horizontal axis, the other end of said upper arm element pivotally connected to one end of said lower arm element and pivotal about a second horizontal axis,

a master support member,

a master control member including an upper arm element and a lower arm element, one end of said upper arm element connected to said master support member and pivotable about a third horizontal axis, the other end of said upper arm element pivotally connected to said lower arm element and pivotal about a fourth horizontal axis,

first servo loop means responsive to the displacements of said lower slave arm element to maintain alignment of the longitudinal axis of said lower slave arm element with the longitudinal axis of said lower master ann element,

second servo loop means responsive to the displacements of said upper slave arm element to maintain alignment of the longitudinal axis of said upper slave arm element with the longitudinal axis of said upper master arm element,

a first force feedback means responsive to torque of said upper slave arm element about said first horizontal axis for applying a corresponding torque reduced in magnitude to said upper master arm element about said third horizontal axis in a direction in opposition to the direction of movement of said upper master arm element producing the torque in said upper slave arm element,

a second force feedback means responsive to torque of said lower slave arm element about said second horizontal axis for applying a corresponding torque reduced in magnitude to said lower master arm element about said forth horizontal axis in a direction in opposition to direction of movement of said lower master arm element producing the torque in said lower slave arm element,

a first lever arm having a pair of ends, one end of which is in fixed relationship to said upper master arm element and movable about said third horizontal axis therewith,

a first support point,

a first flexible tension member,

a first spring member,

one end of said first flexible tension member connected to said other end of said first lever arm and the other end of said first tension member connected to one end of said first spring member, the other end of said first spring member connected to said master support member,

an intermediate portion of said first tension member bearing on said first support point,

the angle less than 180 formed between the a line extending from said other end from said first lever arm member said third horizontal axis and a line extending from and said first support point to said third horizontal axis being equal to the angle less than 180 between the longitudinal axis of said upper arm element and an axis extending vertically upward from said third horizontal axis,

the spring constant of said first spring member being equal to M /a,r,, where M is the moment of the master upper arm element with said lower master arm attached, and the moment of said upper slave arm element with said lower slave arm attached as reflected to said lower master arm element,

a, is the length of the line from said first support point to said third horizontal axis, and

r is the length of said normal from said other end of said first lever arm to said third horizontal axis,

the length of said first tension member being such that the end thereof remote from the end connected to said first spring member when unattached and said first spring member is in its unstressed condition extends to said first support point,

a second lever arm having a pair of ends, one end of which is coincidental with said third horizontal axis and the other end of which is pivotable thereabout,

means for transferring an angular displacement of said lower master arm element with respect to said upper master arm element about said forth horizontal axis to an equal angular displacement of said lever arm about said third horizontal axis,

a second support point,

a second flexible tension member,

a second spring member,

one end of said second flexible tension member connected to said other end of said second lever arm and the other end of said second tension member connected to one end of said second spring member, the other end of said second spring member connected to said master support member, I an intermediate portion of said second tension member bearing on said second support point,

the angle less than fonned between a line extending from said other end of said lever arm member to said third horizontal axis and a line extending from said second support point to said third horizontal axis being equal to the angle less than 180 between the longitudinal axis of said lower arm element and an axis extending vertically upward from said fourth horizontal axis,

the spring constant of said second spring member being equal to M /a r where M is the moment of the lower master arm element and the moment of said lower slave arm element as reflected to said lower master arm element,

a is length of the line from said second support point to said third horizontal axis, and

r is the length of the line from said other end of said second lever arm to said third horizontal axis,

the length of said second tension member being such that the end thereof remote from the end connected to said second spring member when unattached and said second spring member is in its unstressed condition extends to said second support point. 

1. In combination, a slave support member, a slave member, one end of said slave member pivotally connected to said slave support member and pivotal about one horizontal axis, a master support member, a master member, one end of said master member connected to said master support member and pivotable about another horizontal axis, a servo loop means responsive to displacements of said master member to maintain alignment of the longitudinal axis of said slave member with the longitudinal axis of said master member, a force feedback means responsive to torque of said slave member about said one horizontal axis for applying a corresponding torque reduced in magnitude to said master member about said other horizontal axis in a direction in opposition to the direction of movement of said master member producing the torque in said slave member, a lever arm member having a pair of ends, one end of which is in fixed relationship to said master member and movable about said other horizontal axis therewith, a bearing member, a flexible tension member, a spring member, one end of said flexible tension member connected to said other end of said lever arm member and the other end of said tension member connected to one end of said spring member, the other end of said spring member connected to said master support member, an intermeDiate portion of said tension member bearing on a support point of said bearing member on a side thereof remote from said other horizontal axis, the angle less than 180* formed between a line extending from said other end of said lever arm member to said third horizontal axis and a line extending from said support point to said third horizontal axis being equal to the angle less than 180* between the longitudinal axis of said master member and an axis extending vertically upward from said third horizontal axis, the spring constant of said spring member being equal to M/ar, where M is the moment of said master member, and the moment of said slave member as reflected to said master member, a is the length of the line from said support point to said third horizontal axis, and r is the length of the line from said other end of said lever arm to said third horizontal axis.
 2. The combination of claim 1 in which the length of said tension member being such that the end thereof remote from the end connected to said spring member when unattached and said spring member is in its unstressed condition extends to said support point.
 3. In combination, a slave support member, a slave member including an upper arm element and a lower arm element, one end of said upper arm element pivotally connected to said slave support member and pivotal about a first horizontal axis, the other end of said upper arm element pivotally connected to one end of said lower arm element and pivotal about a second horizontal axis, a master support member, a master control member including an upper arm element and a lower arm element, one end of said upper arm element connected to said master support member and pivotable about a third horizontal axis, the other end of said upper arm element pivotally connected to said lower arm element and pivotal about a fourth horizontal axis, first servo loop means responsive to the displacements of said lower slave arm element to maintain alignment of the longitudinal axis of said lower slave arm element with the longitudinal axis of said lower master arm element, second servo loop means responsive to the displacements of said upper slave arm element to maintain alignment of the longitudinal axis of said upper slave arm element with the longitudinal axis of said upper master arm element, a first force feedback means responsive to torque of said upper slave arm element about said first horizontal axis for applying a corresponding torque reduced in magnitude to said upper master arm element about said third horizontal axis in a direction in opposition to the direction of movement of said upper master arm element producing the torque in said upper slave arm element, a second force feedback means responsive to torque of said lower slave arm element about said second horizontal axis for applying a corresponding torque reduced in magnitude to said lower master arm element about said forth horizontal axis in a direction in opposition to direction of movement of said lower master arm element producing the torque in said lower slave arm element, a first lever arm having a pair of ends, one end of which is in fixed relationship to said upper master arm element and movable about said third horizontal axis therewith, a first support point, a first flexible tension member, a first spring member, one end of said first flexible tension member connected to said other end of said first lever arm and the other end of said first tension member connected to one end of said first spring member, the other end of said first spring member connected to said master support member, an intermediate portion of said first tension member bearing on said first support point, the angle less than 180* formed between the a line extending from said other end from said first lever arm member said third horizontal axis and a line extending from and said First support point to said third horizontal axis being equal to the angle less than 180* between the longitudinal axis of said upper arm element and an axis extending vertically upward from said third horizontal axis, the spring constant of said first spring member being equal to MSM/a1r1, where MSM is the moment of the upper master arm element with said lower master arm attached, and the moment of said upper slave arm element with said lower slave arm attached as reflected to said lower master arm element, a1 is the length of the line from said first support point to said third horizontal axis, and r is the length of said normal from said other end of said first lever arm to said third horizontal axis, the length of said first tension member being such that the end thereof remote from the end connected to said first spring member when unattached and said first spring member is in its unstressed condition extends to said first support point, a second lever arm having a pair of ends, one end of which is coincidental with said third horizontal axis and the other end of which is pivotable thereabout, means for transferring an angular displacement of said lower master arm element with respect to said upper master arm element about said forth horizontal axis to an equal angular displacement of said lever arm about said third horizontal axis, a second support point, a second flexible tension member, a second spring member, one end of said second flexible tension member connected to said other end of said second lever arm and the other end of said second tension member connected to one end of said second spring member, the other end of said second spring member connected to said master support member, an intermediate portion of said second tension member bearing on said second support point, the angle less than 180* formed between a line extending from said other end of said lever arm member to said third horizontal axis and a line extending from said second support point to said third horizontal axis being equal to the angle less than 180* between the longitudinal axis of said lower arm element and an axis extending vertically upward from said fourth horizontal axis, the spring constant of said second spring member being equal to MEM/a2r2, where MEM is the moment of the lower master arm element and the moment of said lower slave arm element as reflected to said lower master arm element, a2 is length of the line from said second support point to said third horizontal axis, and r2 is the length of the line from said other end of said second lever arm to said third horizontal axis, the length of said second tension member being such that the end thereof remote from the end connected to said second spring member when unattached and said second spring member is in its unstressed condition extends to said second support point. 